Wave energy, a concentrated form of renewable energy, has many possibilities for supplying energy in an environmentally friendly way. The extraction of wave energy has, at present been left nearly unexploited. This is mostly due to flaws in earlier wave-power plants used to extract this resource. These wave-power plants have often had low efficiency and are often subjected to operational disturbances and damage when exposed to extreme weather conditions.
U.S. Pat. No. 6,476,511 B1 describes a wave-power aggregate consisting of a number of displaced cylinders which are connected in succession by means of hydraulic systems. The hydraulic systems are arranged to extract energy when the adherent cylinders move in proportion to each other due to wave motion. It is understood that the above mentioned aggregate comprises a number of movable parts, such as the hydraulic systems, which result in aggregates of this kind being sensitive to operational disturbance due to for example, corrosion or bad weather conditions.
Furthermore GB 2 024 957 A shows a wave-power aggregate which comprises a number of pipes organized into a raft floating on a water surface and adjusting to wave motion at the surface. The volume of the pipes is arranged to vary when the pipes are stretched, or contracted when the raft moves due to wave motion. In addition, every pipe has one-way valves which makes it possible for water to be pumped through each pipe.
In addition to the above, Offshore Wave Energy Limited has a wave-power aggregate which comprises a container arranged to be placed at sea or lake-water surfaces. When a wave approaches the container, air originating from a trough of sea water will be trapped in the container and pressurized when a following wave crest, covering the opening of the container, travels through the container. The container tails away in the propagation direction of the wave in order to further compress the air. The compressed air can in a later stage for example be converted into electrical energy by means of a generator. The above mentioned aggregate has however certain limitations among others the aggregate cannot utilize energy over an area larger than the opening of the aggregate.
From the exposition above, it is understood that there is a need for developing improved methods and aggregates for extracting energy from wave motion.